[worklets] Introduce ThreadedWorkletMessagingProxy and AnimationWorkletMessagaingProxy.

third_party/WebKit/Source/modules/compositorworker/AnimationWorklet.cpp

 // Copyright 2016 The Chromium Authors. All rights reserved.
 // Use of this source code is governed by a BSD-style license that can be
 // found in the LICENSE file.
 
 #include "modules/compositorworker/AnimationWorklet.h"
 
 #include "bindings/core/v8/V8Binding.h"
+#include "core/dom/Document.h"
 #include "core/frame/LocalFrame.h"
-#include "core/workers/ThreadedWorkletGlobalScopeProxy.h"
+#include "modules/compositorworker/AnimationWorkletMessagingProxy.h"
+#include "modules/compositorworker/AnimationWorkletThread.h"
 
 namespace blink {
 
 // static
 AnimationWorklet* AnimationWorklet::create(LocalFrame* frame)
 {
+    AnimationWorkletThread::ensureSharedBackingThread();
     AnimationWorklet* worklet = new AnimationWorklet(frame);
     worklet->suspendIfNeeded();
     return worklet;
 }
 
 AnimationWorklet::AnimationWorklet(LocalFrame* frame)
     : Worklet(frame)
-    , m_workletGlobalScopeProxy(new ThreadedWorkletGlobalScopeProxy())
+    , m_workletMessagingProxy(new AnimationWorkletMessagingProxy(frame->document()))
 {
+    m_workletMessagingProxy->initialize();
 }
 
 AnimationWorklet::~AnimationWorklet()
 {
+    DCHECK(m_workletMessagingProxy);

[yhirano, 2016/09/12 09:02:58]

Is it good to move this check to the constructor and make m_workletMessageProxy
a const pointer (i.e., ThreadedWorkletMessagingProxy* const
m_workletMessagingProxy)?

[ikilpatrick, 2016/09/12 17:29:07]

sgtm, I've just removed the DCHECK now that it's a const pointer (as gets
created & used right above).

+    m_workletMessagingProxy->parentObjectDestroyed();
 }
 
 WorkletGlobalScopeProxy* AnimationWorklet::workletGlobalScopeProxy() const
 {
-    return m_workletGlobalScopeProxy.get();
+    return m_workletMessagingProxy;
 }
 
 DEFINE_TRACE(AnimationWorklet)
 {
     Worklet::trace(visitor);
 }
 
 } // namespace blink